Paper-based Microfluidic Chip for Detection of 3-Nitrogen in Water Based on Chromogenic Method

Nitrate, nitrite and ammonia nitrogen (3-Nitrogen) are the main pollutants in water. "3-Nitrogen" pollution appears in both surface water and shallow groundwater in China. In this study, we combined the chromogenic method with the microfluidic technology to prepare the chip for simultaneous detection of "3-Nitrogen". Firstly, single.channel paper-based microfluidic chips were fabricated to verify the validity of the detection methods for three nitrogen-containing compounds and to optimize the reaction conditions. The corresponding detection limits were calculated to be 0. 001 mmol/L, 1 mmol/L and 1 mg/L, respectively. In the testing of the actual samples, the spiked recoveries of the three samples were 95. 4% - 114. 9%. Secondly, through a reasonable structural design, the single. channel paper-based microfluidic chips for the detection of three nitrogen-containing compounds were integrated into a multi. channel paper-based microfluidic chip for simultaneous detection of "3-Nitrogen". The detection results obtained by the multi-channel paper- based microfluidic chip maintained good consistency with those of the single.channel paper-based microfluidic chip. The multi.channel paper-based microfluidic chip based on chromogenic method proposed here could simultaneously detect "3-Nitrogen" in water, and the chip had the characteristics of low cost, high sensitivity and easy operation, as well as rapid detection. The technology showed great potential in detection of pollutants in water-contaminated areas with limited resources.